<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 
            先创建一个盒子，宽高一直，用圆角给他50%，变成圆

            在写一个三角形，定位上去，到他中间位置，颜色设为一致，视觉上就是圆锥
        */
        .box {

            width: 100px;
            height: 100px;
            background-color: #f00;
            /* border-left: 70px solid transparent;
            border-right: 70px solid transparent;
            border-top: 100px solid red; */
            /* -moz-border-radius: 50%;
            -webkit-border-radius: 50%; */
            border-radius: 50%;
            position: relative;

        }

        .bom {
            width: 0;
            height: 0;
            border-left: 50px solid transparent;
            border-right: 50px solid transparent;
            border-top: 200px solid #f00;
            position: absolute;
            /* top: -50px;
            left: -30px; */
            top: 50px;
        }
    </style>
</head>

<body>
    <div class="box">
        <!-- 朝下的 -->
        <div class="bom"></div>
    </div>
</body>

</html>